I only watched the first couple minutes, so I'll just comment on that.

Mid harpies are of the utmost importance. After getting the left side mid harpies, you should've checked the right side camp and done it if they were there, HoGing it if needed. You should be running to clear these as soon as these are up. These camps are what allow you to stay ahead of the enemy jungler.

Use your HoG more often. I watched up to your first death, about 6:30 seconds, and you had only used HoG once. You bought the skill, so get the most out of it!

Put one point into your escape ability before level 5. Assuming you had your leap, you would have been able to pounce on the Kali, or leap away from Cupid since his dash was on cooldown.

And to restate it for emphasis, you should prioritize the mid harpy camps over all other camps. It gets you gold and EXP, and denies the opportunity to the enemy. Unless something really wonky happens early, after you clear the 2 ogre camps on one side and both small harpy camps, then the mid harpy camps will be spawning soon. At 4:00 you chose to get the speed camp when you should have been going to check on the mid harpies. You should be able to get there before they respawn. If they are not there then you can hand out for a few seconds and nab them right away. You can go back to get speed after. The damage buff should be falling off right about now. I like to get his leap second because it allows you to bypass a lot of walls. It speeds up the clearing process a great deal.

I watched the first five minutes of your video.
First thing I noticed:
You bought Hand of the Gods. Why didn't you use it then (earlier)? ;)

You cleared the mid harpies with your team, good beginning. Then you went to Red with Hel. You should have used HoG on it. That way the camp would have been cleared faster, you had the buff earlier and Hel could have returned to her lane earlier.
Then you get Blue for (and with) Hel and after that you clear the back/rear Harpies. Good. After that you get Orange. Here you are using HoG for the first time.

I think you saved it for when you are quite low on health. But if you would have used it on Red earlier, you could have used it on Orange for the 2nd time already because the cooldown is quite short.

You're skipping other Blue then and take Mid Harpies again instead. Just like I am doing it.

Next thing.. about your build. You're going for a lot of potions. In my humble opinion you're missing physical power in the beginning. Okay, okay, you have HoG. But instead you can try buying a early Potion of Physical Might (that 400 gold potion) instead (+ 1 Health Potion). It's Bumbas + Boots Lv1 + 2 Health Pots for me or Bumbas + Potion of Phys Might + HoG + 1 Health Pot. If you are using the PoPM you really want to make sure that you don't die early.

Try watching the tournamets on Saturday/Sunday to learn. Watching the junglers of top teams really helped me.

Oh, one more thing. You can safe two seconds by not not moving and typing "speed" but instead just ping it on the map while continuing to walk. (I think you know how to.. but just in case you don't, press and hold space and click on the mini map). For me pinging works better. :)
(Edit: Just noticed Space bar is Active 1 for you.. so it would be a different key for you)

As I said, I'm not a pro either, I am rarely jungling. But I just went 11-0-6 with Bastet with the latter build and I am frickin' proud of it. :P

Watching the rest of the vid... well, everything that follows is basically backseat gaming I assume.

I would have put the third or fourth skill point in the escape ability. I think this is what you wanted to do anyway. Before you died for the first time after your Kali mid lane gank thingy... you could have easily jumped away that way.
But you're right. Not killing Kali was really unfortunate. But as Fenrir you have a hard time against Kali anyway in my opinion since she can easily use her ultimate to get out of your ultimate. There are better targets for Fenrir's ultimate.

I think your second death... it was due to using Brutalize that close to the enemy tower. Not really a good idea. :D
Chronos simply walks into tower range and you're automatically getting shot by it and it's doing a lot of damage early game.
Oh, you are not dying in that situation. Using Brutalize was really risky.

But you are dying shortly after: when trying to grab Red, Cupid ganks you. This could have been avoided by better map awareness. In the video you can clearly see on the mini map that Cupid is chasing you into the jungle. Backseat gaming as I said. My map awareness is horrible. But watching the video.. the death could have been avoided.
By the way your Hand of the Gods was up. If you would have used it, Cupid at least wouldn't have gotten Red. ;)

I like picking easy targets for my first gank. All of the gods you played against had escape abilites but I think Kali and Chronos are the hardest target, at least for a Fenrir because they can simply nullify your ultimate by using their ultimate.

At 12:20 you tried to gank but the enemies died before you arrived. Since you were in the "enemy jungle" anyway you could have used the situation and steal some of the enemy jungle. At least the mana buff, because they were four man down, you walked right next to it and also your HoG was up. :)

Instead you roamed a bit... (I'm doing the same sometimes, don't worry. Decision making as a jungler is hard in the beginning I feel) and then you tried to fight Chronos. That's okay. You ran away when enemy Athena joined the fight. Good. BUT. You could have easily jumped out again using your 1, avoided Chronos' 1 and more importantly his follow-up stun and could have avoided death.
You did so at 14:30 by the way. You prepared the jump because you were low on health. So obviously you already know how to escape, hehe. Guess it was the live commentary then. Talking while playing can sometimes be really distracting, hehe.

This was awesome feedback and I've definitely got a lot to think about ... I've watched it back myself now with these comments in mind and it all seems so obvious to me now but I guess thats a good thing

That early build with physical potion sound like such a better plan and is something I definitely want to try out!

I usally watch the streams with Drybear and squiidish and that but they usually give an overview of the entire game rather than just the jungler :)

thanks again for this massive response and be sure I'm going to check back to it as I'm sure a lot of it will be forgotten to begin with lol :D

Glad to hear. :)
Drybear is awesome, hehe. I learned a lot from dmbrandon's streams but I check out dry's youtube channel every now and then, too.

And as I said the tournaments. The phys potion was an EU tourny thing and when I tried it it just worked out so well... the clear was so insanely fast together with HoG. :)
Use HoG whenever it is up. Not on Harpies though in my opinion. Except you want to steal it from the enemy. :D